src/tools/clippy/clippy_lints/src/exhaustive_items.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::source::indent_of;
   3 use if_chain::if_chain;
   4 use rustc_errors::Applicability;
   5 use rustc_hir::{Item, ItemKind};
   6 use rustc_lint::{LateContext, LateLintPass};
   7 use rustc_session::{declare_lint_pass, declare_tool_lint};
   8 use rustc_span::sym;
   9
  10 declare_clippy_lint! {
  11     /// ### What it does
  12     /// Warns on any exported `enum`s that are not tagged `#[non_exhaustive]`
  13     ///
  14     /// ### Why is this bad?
  15     /// Exhaustive enums are typically fine, but a project which does
  16     /// not wish to make a stability commitment around exported enums may wish to
  17     /// disable them by default.
  18     ///
  19     /// ### Example
  20     /// ```rust
  21     /// enum Foo {
  22     ///     Bar,
  23     ///     Baz
  24     /// }
  25     /// ```
  26     /// Use instead:
  27     /// ```rust
  28     /// #[non_exhaustive]
  29     /// enum Foo {
  30     ///     Bar,
  31     ///     Baz
  32     /// }
  33     /// ```
  34     pub EXHAUSTIVE_ENUMS,
  35     restriction,
  36     "detects exported enums that have not been marked #[non_exhaustive]"
  37 }
  38
  39 declare_clippy_lint! {
  40     /// ### What it does
  41     /// Warns on any exported `structs`s that are not tagged `#[non_exhaustive]`
  42     ///
  43     /// ### Why is this bad?
  44     /// Exhaustive structs are typically fine, but a project which does
  45     /// not wish to make a stability commitment around exported structs may wish to
  46     /// disable them by default.
  47     ///
  48     /// ### Example
  49     /// ```rust
  50     /// struct Foo {
  51     ///     bar: u8,
  52     ///     baz: String,
  53     /// }
  54     /// ```
  55     /// Use instead:
  56     /// ```rust
  57     /// #[non_exhaustive]
  58     /// struct Foo {
  59     ///     bar: u8,
  60     ///     baz: String,
  61     /// }
  62     /// ```
  63     pub EXHAUSTIVE_STRUCTS,
  64     restriction,
  65     "detects exported structs that have not been marked #[non_exhaustive]"
  66 }
  67
  68 declare_lint_pass!(ExhaustiveItems => [EXHAUSTIVE_ENUMS, EXHAUSTIVE_STRUCTS]);
  69
  70 impl LateLintPass<'_> for ExhaustiveItems {
  71     fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
  72         if_chain! {
  73             if let ItemKind::Enum(..) | ItemKind::Struct(..) = item.kind;
  74             if cx.access_levels.is_exported(item.def_id);
  75             let attrs = cx.tcx.hir().attrs(item.hir_id());
  76             if !attrs.iter().any(|a| a.has_name(sym::non_exhaustive));
  77             then {
  78                 let (lint, msg) = if let ItemKind::Struct(ref v, ..) = item.kind {
  79                     if v.fields().iter().any(|f| !f.vis.node.is_pub()) {
  80                         // skip structs with private fields
  81                         return;
  82                     }
  83                     (EXHAUSTIVE_STRUCTS, "exported structs should not be exhaustive")
  84                 } else {
  85                     (EXHAUSTIVE_ENUMS, "exported enums should not be exhaustive")
  86                 };
  87                 let suggestion_span = item.span.shrink_to_lo();
  88                 let indent = " ".repeat(indent_of(cx, item.span).unwrap_or(0));
  89                 span_lint_and_then(
  90                     cx,
  91                     lint,
  92                     item.span,
  93                     msg,
  94                     |diag| {
  95                         let sugg = format!("#[non_exhaustive]\n{}", indent);
  96                         diag.span_suggestion(suggestion_span,
  97                                              "try adding #[non_exhaustive]",
  98                                              sugg,
  99                                              Applicability::MaybeIncorrect);
 100                     }
 101                 );
 102
 103             }
 104         }
 105     }
 106 }